Optical (de)multiplexers

Abstract

An optical demultiplexer/multiplexer, comprising: a multimode interference waveguide; at least one first coupling waveguide which meets the multimode interference waveguide at least one first location and a plurality of second coupling waveguides which meet the multimode interference waveguide at a plurality of second locations which are spaced in a direction of transmission in relation to the at least one first location, with the at least one first coupling waveguide and the second coupling waveguides together with the multimode interference waveguide providing a first angled multimode interferometer which operates to demultiplex a first optical signal having optical channels of a plurality of wavelengths or multiplex optical signals of a plurality of wavelengths into a first optical signal having optical channels of the plurality of wavelengths; at least one third coupling waveguide which meets the multimode interference waveguide at least one third location and a plurality of fourth coupling waveguides which meet the multimode interference waveguide at a plurality of fourth locations which are spaced in a direction of transmission in relation to the at least one third location, with the at least one third coupling waveguide and the plurality of fourth coupling waveguides together with the multimode interference waveguide providing a second angled multimode interferometer which operates to demultiplex a second optical signal having optical channels of a plurality of wavelengths or multiplex optical signals of a plurality of wavelengths into a second optical signal having optical channels of the plurality of wavelengths; whereby the demultiplexer/multiplexer provides for the demultiplexing/multiplexing of first and second optical signals having optical channels of a plurality of wavelengths. In a further embodiment the first coupling waveguide of an optical demultiplexer/multiplexer comprising a first angled multimode interferometer is stepped or tapered in order to couple a signal having a broadened spatial, or spectral, profile. In another embodiment of an optical demultiplexer/multiplexer comprising a first angled multimode interferometer a plurality of first coupling waveguides are coupled to a photonic structure which provides a plurality of output signals having substantially equal intensity and a phase difference, also in order to couple a signal or signals having a broadened spatial, or spectral, profile. In yet another embodiment of an optical demultiplexer/multiplexer comprising a first angled multimode interferometer the multimode interference waveguide includes a reflector at one end.

The invention claimed is: 
     
       1. An optical demultiplexer/multiplexer, comprising:
 a multimode interference waveguide; 
 at least one first coupling waveguide which meets the multimode interference waveguide at least one first location and a plurality of second coupling waveguides which meet the multimode interference waveguide at a plurality of second locations which are spaced in a direction of transmission in relation to the at least one first location, with the at least one first coupling waveguide and the second coupling waveguides together with the multimode interference waveguide providing a first angled multimode interferometer which operates to demultiplex a first optical signal having optical channels of a plurality of wavelengths or multiplex optical signals of a plurality of wavelengths into a first optical signal having optical channels of the plurality of wavelengths; 
 at least one third coupling waveguide which meets the multimode interference waveguide at least one third location and a plurality of fourth coupling waveguides which meet the multimode interference waveguide at a plurality of fourth locations which are spaced in a direction of transmission in relation to the at least one third location, with the at least one third coupling waveguide and the plurality of fourth coupling waveguides together with the multimode interference waveguide providing a second angled multimode interferometer which operates to demultiplex a second optical signal having optical channels of a plurality of wavelengths or multiplex optical signals of a plurality of wavelengths into a second optical signal having optical channels of the plurality of wavelengths; 
 whereby the demultiplexer/multiplexer provides for the demultiplexing/multiplexing of first and second optical signals having optical channels of a plurality of wavelengths. 
 
     
     
       2. The demultiplexer/multiplexer of  claim 1 , wherein (i) the first and second coupling waveguides are coupled to opposite sides of the multimode interference waveguide, or (ii) the first and second coupling waveguides are coupled to a single, common side of the multimode interference waveguide. 
     
     
       3. The demultiplexer/multiplexer of  claim 1 , wherein (i) the third and fourth coupling waveguides are coupled to opposite sides of the multimode interference waveguide, or (ii) the third and fourth coupling waveguides are coupled to a single, common side of the multimode interference waveguide. 
     
     
       4. The demultiplexer/multiplexer of  claim 1 , wherein (i) the first and third coupling waveguides are coupled to a single, common side of the multimode interference waveguide, or (ii) the first and third coupling waveguides are coupled to opposite sides of the multimode interference waveguide. 
     
     
       5. The demultiplexer/multiplexer of  claim 1 , wherein (i) the second and fourth coupling waveguides are coupled to a single, common side of the multimode interference waveguide, or (ii) the second and fourth coupling waveguides are coupled to opposite sides of the multimode interference waveguide. 
     
     
       6. The demultiplexer/multiplexer of  claim 1 , wherein (i) the first and second angled multimode interferometers have a single, common transmission direction, or (ii) a transmission direction of the first angled multimode interferometer is opposite to a transmission direction of the second angled multimode interferometer. 
     
     
       7. The demultiplexer/multiplexer of  claim 1 , wherein (i) the at least one first coupling waveguide is coupled to an endwall of the multimode interference waveguide, (ii) the at least one first coupling waveguide is coupled to a sidewall of the multimode interference waveguide, or (iii) the at least one first coupling waveguide is coupled to a junction of a sidewall and an endwall of the multimode interference waveguide. 
     
     
       8. The demultiplexer/multiplexer of  claim 1 , wherein the at least one first coupling waveguide is configured to couple a signal between the at least one first coupling waveguide and the multimode interference waveguide which has a broadened spatial profile, optionally having a substantially flat-top spectral profile, optionally the at least one first coupling waveguide has a stepped or tapered waveguide, whereby the at least one first coupling waveguide couples an optical signal between the at least one first coupling waveguide and the multimode interference waveguide which has a broadened spatial profile, optionally having a substantially flat-top spectral profile. 
     
     
       9. The demultiplexer/multiplexer of  claim 1 , comprising:
 a plurality of first coupling waveguides at a plurality of first locations which are spaced in the direction of transmission for the first angled multimode interferometer; and 
 a first photonic structure which provides a plurality of output signals which have substantially equal intensity and a phase and/or polarization difference, optionally the first photonic structure comprises an imbalanced Mach-Zehnder Interferometer (MZI) having outputs which are coupled to respective ones of the first coupling waveguides. 
 
     
     
       10. The demultiplexer/multiplexer of  claim 1 , wherein (i) the at least one third coupling waveguide is coupled to an endwall of the multimode interference waveguide, (ii) the at least one third coupling waveguide is coupled to a sidewall of the multimode interference waveguide, or (iii) the at least one third coupling waveguide is coupled to a junction of a sidewall and an endwall of the multimode interference waveguide. 
     
     
       11. The demultiplexer/multiplexer of  claim 1 , wherein the at least one third coupling waveguide is configured to couple a signal between the at least one third coupling waveguide and the multimode interference waveguide which has a broadened spatial profile, optionally having a substantially flat-top spectral profile, optionally the at least one third coupling waveguide has a stepped or tapered waveguide, whereby the at least one third coupling waveguide couples an optical signal between the at least one third coupling waveguide and the multimode interference waveguide which has a broadened spatial profile, optionally having a substantially flat-top spectral profile. 
     
     
       12. The demultiplexer/multiplexer of  claim 1 , comprising:
 a plurality of third coupling waveguides at a plurality of third locations which are spaced in the direction of transmission for the second angled multimode interferometer; and 
 a second photonic structure which provides a plurality of output signals which have substantially equal intensity and a phase and/or polarization difference, optionally the second photonic structure comprises an imbalanced Mach-Zehnder Interferometer (MZI) having outputs which are coupled to respective ones of the third coupling waveguides. 
 
     
     
       13. The demultiplexer/multiplexer of  claim 1 , wherein (i) the first and second angled multimode interferometers are each configured to operate as a demultiplexer, (ii) the first and second angled multimode interferometers are each configured to operate as a multiplexer, or (iii) one of the first and second angled multimode interferometers is configured to operate as a demultiplexer and the other of the first and second angled multimode interferometers is configured to operate as a multiplexer. 
     
     
       14. The demultiplexer/multiplexer of  claim 1 , wherein (i) at least one of or each of the first and second angled multimode interferometers are configured to provide for wavelength division (de)multiplexing, (ii) at least one of or each of the first and second angled multimode interferometers are configured to provide for polarization (de)multiplexing, or (iii) at least one of or each of the first and second angled multimode interferometers are configured to provide for wavelength division and polarization (de)multiplexing. 
     
     
       15. The demultiplexer/multiplexer of  claim 1 , wherein the demultiplexer/multiplexer is a semiconductor structure, optionally implemented in a semiconductor-on-insulator (SOI) structure. 
     
     
       16. An optical demultiplexer/multiplexer, comprising:
 a multimode interference waveguide; 
 a plurality of first coupling waveguides which meet the multimode interference waveguide at a plurality of first locations and a plurality of second coupling waveguides which meet the multimode interference waveguide at a plurality of second locations which are spaced in a direction of transmission in relation to the first locations, with the first and second coupling waveguides together with the multimode interference waveguide providing an angled multimode interferometer which operates to demultiplex an optical signal having optical channels of a plurality of wavelengths and/or polarizations or multiplex optical signals of a plurality of wavelengths and/or wavelengths into an optical signal having optical channels of the plurality of wavelengths and/or polarizations; 
 wherein the first coupling waveguides are configured to receive optical signals having different wavelength and/or polarization components, each comprising optical channels having a plurality of wavelengths and/or polarizations, and provide for a broadened spatial profile, optionally having a substantially flat-top spectral profile, to signals transmitted between the first and second coupling waveguides; 
 optionally the first coupling waveguides are coupled to a photonic structure which provides a plurality of output signals which have substantially equal intensity and a phase and/or polarization difference, optionally the photonic structure comprises an imbalanced Mach-Zehnder Interferometer (MZI) having outputs which are coupled to respective ones of the third coupling waveguides. 
 
     
     
       17. An optical demultiplexer/multiplexer, comprising:
 a multimode interference waveguide, wherein the multimode interference waveguide includes a first reflector at one end in a first direction of transmission which acts to reflect an optical signal or signals in a second direction of transmission which is opposite to the first direction of transmission; and 
 at least one first coupling waveguide which meets the multimode interference waveguide at least one first location and a plurality of second coupling waveguides which meet the multimode interference waveguide at a plurality of second locations, with the at least one first coupling waveguide and the plurality of second coupling waveguides together with the multimode interference waveguide providing a first angled multimode interferometer which operates to demultiplex a first optical signal having optical channels of a plurality of wavelengths and/or polarizations or multiplex optical signals of a plurality of wavelengths and/or polarizations into a first optical signal having optical channels of the plurality of wavelengths and/or polarizations. 
 
     
     
       18. The demultiplexer/multiplexer of  claim 17 , wherein the first reflector comprises a reflective film or layer. 
     
     
       19. The demultiplexer/multiplexer of  claim 17 , wherein (i) the first and second coupling waveguides are coupled to opposite sides of the multimode interference waveguide, or (ii) the first and second coupling waveguides are coupled to a single, common side of the multimode interference waveguide. 
     
     
       20. The demultiplexer/multiplexer of  claim 17 , wherein (i) the first angled multimode interferometer is configured to operate as a demultiplexer, or (ii) the first angled multimode interferometer is configured to operate as a multiplexer. 
     
     
       21. The demultiplexer/multiplexer of  claim 17 , further comprising:
 at least one third coupling waveguide which meets the multimode interference waveguide at least one third location and a plurality of fourth coupling waveguides which meet the multimode interference waveguide at a plurality of fourth locations, with the at least one third coupling waveguide and the plurality of fourth coupling waveguides together with the multimode interference waveguide providing a second angled multimode interferometer which operates to demultiplex a second optical signal having optical channels of a plurality of wavelengths and/or polarizations or multiplex optical signals of a plurality of wavelengths and/or polarizations into a second optical signal having optical channels of the plurality of wavelengths and/or polarizations; 
 optionally (i) the third and fourth coupling waveguides are coupled to opposite sides of the multimode interference waveguide, or (ii) the third and fourth coupling waveguides are coupled to a single, common side of the multimode interference waveguide. 
 
     
     
       22. The demultiplexer/multiplexer of  claim 17 , wherein (i) the second angled multimode interferometer is configured to operate as a demultiplexer, or (ii) the second angled multimode interferometer is configured to operate as a multiplexer. 
     
     
       23. The demultiplexer/multiplexer of  claim 17 , wherein (i) the first and third coupling waveguides are coupled to a single, common side of the multimode interference waveguide, or (ii) the first and third coupling waveguides are coupled to opposite sides of the multimode interference waveguide. 
     
     
       24. The demultiplexer/multiplexer of  claim 17 , wherein (i) the second and fourth coupling waveguides are coupled to a single, common side of the multimode interference waveguide, or (ii) the second and fourth coupling waveguides are coupled to opposite sides of the multimode interference waveguide. 
     
     
       25. The demultiplexer/multiplexer of  claim 17 , wherein (i) the first and second angled multimode interferometers have a single, common input transmission direction, or (ii) the multimode interference waveguide includes a second reflector at an opposite, other end to the first reflector, which acts to reflect an optical signal or signals in the first direction of transmission, and the input transmission direction of the first angled multimode interferometer is opposite to the input transmission direction of the second angled multimode interferometer, optionally the second reflector comprises a reflective film or layer. 
     
     
       26. The demultiplexer/multiplexer of  claim 17 , wherein the demultiplexer/multiplexer is a semiconductor structure, optionally implemented in a semiconductor-on-insulator (SOI) structure. 
     
     
       27. An optical transceiver incorporating the at least one demultiplexer/multiplexer of  claim 1 . 
     
     
       28. An optical sensor incorporating the at least one demultiplexer/multiplexer of  claim 1 . 
     
     
       29. A method of using the demultiplexer/multiplexer of  claim 1 , optionally (a) the first and second angled multimode interferometers each operate as demultiplexers, (b) the first and second angled multimode interferometers each operate as multiplexers, or (c) one of the first and second angled multimode interferometers operates as a demultiplexer and the other of the first and second angled multimode interferometers operates as a multiplexer.